New homebrewer here. About 3 weeks ago I bottled my first ever batch, a cranberry saison for the holiday season. The flavor is pretty great to me but the two bottles I’ve tested (one at 2 weeks, and one at 3 weeks) didn’t have nearly enough carbonation. I most likely forgot to change the unit on my scale and didn’t use enough priming sugar. I used flip top bottles because I got a ton for free.
Is there a safe way to increase carbonation a little bit without truly knowing how much I put in originally?
Given that they are flip tops, why not give ‘er a try with a few and learn something? Make a simple sugar syrup, let it cool, pop open a few bottles and put some in. Try to keep things sanitary and take notes. Assuming you made a decent sized batch, I think trying it out on a few bottles is worth it as a learning opportunity. Just don’t add more than say a 1/2 tsp of syrup to a 12/16 oz. bottle to prevent “bottle bombs” and cool them down well before opening carefully. If you are worried, start trying them after 4-5 days to get an idea of how much carbonation you are getting. If it’s gets too high; open the bottles you re-primed and sacrifice those to the sink drain.
You didn’t happen to put the primed bottles directly in the fridge or cold cellar did you? If so they could easily have not finished carbing in 3 weeks. If that is the case get them to room temp in check in a week.
I once had a stuck fermation that I believe was caused by a temperature fluctuation similar to the temp range you describe in your garage. I think it is worth a shot to keep them in the warmest spot in your house, wrapped in a towel or blanket if it gets cold overnight, and see what happens in a week. Also, lightly swirl them around to rouse the yeast. There is nothing to lose.